Wittgenstein's thing (Tractatus 5.42) about the interdefinability of the logical connectives revealing that they are not basic - where perhaps ab-Notation, or truth-tables considered as propositions, are - is striking, and seems like it might contain some insight. However, what about the quantifiers and the modalities?! Do these not just show the underlying principle in question to be in error? And if so, then what is there in Wittgenstein's remark, which feels insighful? Or is it just a sheer mistake?